Compounds of boron have been used as preservatives for timber for many years. Typically such compounds of boron are applied to timber to be treated by dipping of the timber in a bath or the like comprising of an aqueous solution of the boron compound. After, dipping the timber must remain under non-drying conditions for sufficient time for the boron to diffuse into the timber, which can be of the order of weeks or some months, and thus the preservation process is relatively time consuming. In commercial terms it is desirable to minimise standing time for timber stocks.
The more rapid preservative treatment of timber with a boron compound by treating the timber with the boron preservative in the vapour phase is known. Some compounds of boron are either low boiling point liquids or gases. When placed in contact with timber or wood-based products, selected compounds undergo chemical reaction with the wood or residual wood moisture whereby boron as compounds of boron is deposited in the timber. For example, on contact with wood trimethyl borate reacts, it is believed with wood moisture, to deposit in the wood material as boric acid.